There are many sawmills near Williams Lake, British Columbia. Before the TransCanada Power L.P. power plant was built, a large portion of the wood residues was burned in beehive burners, with no useful heat output. Now these residues are burned in a much more environmentally friendly way. The biomass fuel is sawdust, shavings and bark, with a moisture content well below that generally found in many pulp mills. The shavings, from a local kiln-dried lumber plant, play a large part in bringing the moisture level down. The boiler uses a water-wall furnace and a water-cooled vibrating hydro-grate, which allows the use of high temperature (260°C, or 500°F) combustion air. The boiler is rated at 610 000 pounds (277 tons) per hour at 1550 psig pounds per square inch (10,700 kilopascals) 510°C (950°F) and the condensing steam turbine is rated at 66 megawatts but can produce up to 75 megawatts of electric power. TransCanada operates the largest biomass-fired boiler/turbine unit in Canada that is not located at a pulp and paper mill. In this case, the main driver was the province’s desire to stop the burning of wood residues in beehive burners. The integrated electric power utility owned by the provincial government, BC Hydro, entered into a premium power purchase arrangement with the biomass plant. The economics are not as good as they are for similar systems at pulp mills, however; in the pulp mill case, the steam plant operators have responsibilities beyond steam and power generation, so some of their costs can be allocated to other departments. The power plant is within easy reach of nearby sawmills and could sell steam to them for use in dry kilns, but this would reduce electric power output. The company earns more money by utilizing all of the steam to generate electric power. At the time it was built, this plant would not have been viable without a special long-term electric power contract with BC Hydro. This arrangement has solved an environmental problem, created 43 full-time jobs and improved the competitiveness as well as the stability of the sawmills.

© Minister of Natural Resources Canada 1997-2009
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